The partial turn type fastener is well established in the art as a device for fastening a pair of panels or a panel to a supporting structure together and for its removal by a rapid simple movement, eg. a partial turn on a screw or handle. This type of fastener is found in use in removable panels of aircraft and other vehicles and in electronic equipment housings as well. Often a number of fasteners are used to hold a single panel in place and each is locked or unlocked by the partial turn movement. Usually a partial turn clockwise locks the device and a partial turn counter clockwise unlocks it. Characteristically, these devices have an internal spring which partially ejects the head or locking member when in an unlocked position so that viewing a panel from a reasonable distance, any unlocked fasteners are are easily visible by the protruding head portion.
Most of the partial turn fasteners employ a resilient spring member to apply the locking or fastening force to the panels. As an example, a key like member on the end of a locking stud is inserted through the panels and through a resilient saddle like member. By a partial turn of the locking stud, the key portions engage the resilient saddle and, employing the spring characteristics of the saddle, lock the panels together. Typical of such type of locking device is U.S. Pat. No. 2,640,244, FIGS. 1-4 and U.S. Pat. Nos. 2,839,808 and 2,843,907 to Zahodiakin. These latter two patents and FIGS. 5-12 of the Becker U.S. Pat. No. 2,640,244 also disclose the use of an internal locking nut which cooperates with the stud.
U.S. Pat. No. 2,922,211 to Boyd shows such a locking stud which engages a threaded sleeve.
In each of these representative prior art devices, plus all devices of art with which the applicant is familiar, the fastening device either obtains its fastening strength or force through the resiliency of the spring like member such that with aging, temperature changes, crystallization or other variations, the locking forces vary. As an alternative where a direct screw nut connection is achieved, it is possible to back the screw off without releasing the panels until the screw is totally removed. This defeats the purpose of partial turn release.